Schallmo Michael-Paul, Kale Alex M, Murray Scott O
Department of Psychology, University of Washington, Seattle, WA, USA.
Department of Psychiatry and Behavioral Science, University of Minnesota, Minneapolis, MN, USA.
J Vis. 2019 Apr 1;19(4):12. doi: 10.1167/19.4.12.
What we see depends on the spatial context in which it appears. Previous work has linked the suppression of perceived contrast by surrounding stimuli to reduced neural responses in early visual cortex. This surround suppression depends on at least two separable neural mechanisms, "low-level" and "higher level," which can be differentiated by their response characteristics. We used electroencephalography to demonstrate for the first time that human occipital neural responses show evidence of these two suppression mechanisms. Eighteen adults (10 women, 8 men) each participated in three experimental sessions, in which they viewed visual stimuli through a mirror stereoscope. The first session was used to identify the C1 component, while the second and third comprised the main experiment. Event-related potentials were measured in response to center gratings either with no surround or with surrounding gratings oriented parallel or orthogonal, and presented in either the same eye (monoptic) or the opposite eye (dichoptic). We found that the earliest component of an event-related potential (C1; ∼60 ms) was suppressed by surrounding stimuli, but that suppression did not depend on surround configuration. This suggests a suppression mechanism that is not tuned for relative orientation acting on the earliest cortical response to the target. A later response component (N1; ∼160 ms) showed stronger suppression for parallel and monoptic surrounds, consistent with our earlier psychophysical results and a second form of suppression that is binocular and orientation tuned. We conclude that these two forms of surround suppression have distinct response time courses in the human visual system, which can be differentiated using electrophysiology.
我们所看到的取决于其呈现的空间背景。先前的研究工作已将周围刺激对感知对比度的抑制与早期视觉皮层中神经反应的减少联系起来。这种周围抑制至少依赖于两种可分离的神经机制，即“低级”和“高级”机制，它们可通过其反应特征加以区分。我们首次利用脑电图证明，人类枕叶神经反应显示出这两种抑制机制的证据。18名成年人（10名女性，8名男性）每人参加了三个实验环节，在这些环节中他们通过镜像立体镜观看视觉刺激。第一个环节用于识别C1成分，而第二个和第三个环节构成主要实验。测量了与事件相关的电位，以响应无周围刺激的中心光栅，或具有平行或正交取向的周围光栅，并以单眼（同侧眼）或双眼（对侧眼）呈现。我们发现，与事件相关电位的最早成分（C1；约60毫秒）受到周围刺激的抑制，但这种抑制并不取决于周围刺激的配置。这表明存在一种对相对取向不敏感的抑制机制，作用于对目标的最早皮层反应。稍后的反应成分（N1；约160毫秒）对平行和单眼周围刺激表现出更强的抑制，这与我们早期的心理物理学结果一致，也是一种双眼且对取向敏感的第二种抑制形式。我们得出结论认为，这两种周围抑制形式在人类视觉系统中具有不同的反应时间进程，可利用电生理学加以区分。
